1. Field of the Invention
The present invention relates to a line head for an ink-jet printer and, more particularly, to a line head of an ink-jet printer, in which capacity of an ink chamber filled with an ink is changed by a piezoelectric actuator and a required printing is performed with the ink-jetted at this moment from an ink nozzle through an ink passage. Such a line head is used in the form of being incorporated in various ink-jet printers such as word processor, facsimile, plotter.
2. Prior art
In the field of printers such as word processor, facsimile, plotter, ink-jet printers using a piezoelectric actuator have been already put into practical use, and there are several types of them.
As one type of the ink-jet printer, Kaiser type is known as is disclosed in the specifications of U.S. Pat. Nos. 4,189,734 and 4,216,483, etc., for example. The Kaiser type printer head is generally constructed in the following manner. That is, on a base of the printer head, separate ink passages branched from a common ink passage are provided toward injection nozzles. Further on the base of the printer head, a vibration plate is mounted in such a manner as to cover the separate ink passages. By vibrating this vibration plate flexibly, capacity of each ink passage is changed, and an ink is jetted toward a paper for each vibration of the vibration plate. To give a vibration driving force to the vibration plate, piezoelectric elements are secured to the vibration plate respectively at positions corresponding to the separate ink passages. By applying a voltage to a selected piezoelectric element, the piezoelectric element is displaced to vibrate the vibration plate at the portion. As a result, capacity of the separate ink passages at the portion corresponding to the vibration of the vibration plate is changed as mentioned above so that the ink is forced out of the injection nozzles.
Improvements have been further applied from various viewpoints to the ink-jet printer of Kaiser type of above construction, as is disclosed in the Japanese Laid-Open Patent Publication (unexamined) Sho 63-252750, specifications of corresponding U.S. Pat. Nos. 4,879,568, 4,887,100, 4,992,808, 5,003,679, 5,028,936, etc. It is said that such improved printer heads make it possible to provide an ink-jet printer capable of operating with a low energy and in which ink-jet density is high.
In the recent ink-jet printers, however, a higher level of printing speed and print quality have been increasing demanded, and with the line head of mentioned Kaiser type printer, it is rather difficult to satisfy such a demand of high printing speed and high print quality. In other words, under the conventional technology, there is a limit in applying a fine machining or processing to ink head, and it is now quite difficult to achieve a highly fine and delicate processing in the aspects of pitch and size of ink nozzles and ink passages.
In the prior art, it is also impossible to apply a fine processing to a piezoelectric element of ferroelectric substance. Moreover, under the conventional technology, as number of nozzles is small, reproducibility of original image is poor.
Under such circumstances, multicolor printing with five colors or more is difficult in the prior art. It is also difficult to achieve a high speed printing and a high print quality with the line head manufactured according to the prior art. In other words, if it becomes possible to provide a line head for ink-jet printer applied with a highly fine processing, multicolor printing will become possible, and not only a reproduction of original image with a high fidelity but also a high speed printing will be achieved.